Abstract
We present a novel method of reducing the footprint and increasing the efficiency of the modern multi-MW rf pulse compressor. This system utilizes a high power rf polarizer to couple two circular waveguide modes in quadrature to a single resonant cavity in order to replicate the response of a traditional two cavity configuration using a 4-port hybrid. The 11.424 GHz, high-Q, spherical cavity has a 5.875 cm radius and is fed by the circularly polarized signal to simultaneously excite the degenerate $T{E}_{114}$ modes. The overcoupled spherical cavity has a ${Q}_{0}$ of $9.4\ifmmode\times\else\texttimes\fi{}{10}^{4}$ and coupling factor ($\ensuremath{\beta}$) of 7.69 thus providing a loaded quality factor ${Q}_{L}$ of $1.06\ifmmode\times\else\texttimes\fi{}{10}^{4}$ with a fill time of 150 ns. Cold tests of the polarizer demonstrated good agreement with the numerical design, showing transmission of $\ensuremath{-}0.05\text{ }\text{ }\mathrm{dB}$ and reflection back to the input rectangular WR 90 waveguide less than $\ensuremath{-}40\text{ }\text{ }\mathrm{dB}$ over a 100 MHz bandwidth. This novel rf pulse compressor was tested at SLAC using XL-4 Klystron that provided rf power up to 32 MW and generated peak output power of 205 MW and an average of 135 MW over the discharged signal. A general network analysis of the polarizer is discussed as well as the design and high power test of the rf pulse compressor.
Highlights
High power microwave (HPM) devices are used in multiple scientific and industrial applications including particle accelerators, communication, and defense technology [1,2]
Radio frequency pulse compression is often utilized to alleviate this cost by transforming a low power, long pulse, input signal to a higher power, short pulse, output
Radio frequency pulse compression is a mature technology which can be accomplished through several different methods [3,4,5]
Summary
High power microwave (HPM) devices are used in multiple scientific and industrial applications including particle accelerators, communication, and defense technology [1,2]. Existing embodiments of the polarizer, require the use of complicated structures such as irises, septums, or corrugations, in order to properly excite the circularly polarized output signal [9,10,11] These features can increase electromagnetic fields and significantly reduce the devices power handling capabilities due to heating and breakdown. The rf polarizer presented here is a compact device that utilizes only smooth, rounded, surfaces to minimize this enhancement while maintaining the inherent high power handling capabilities of an overmoded system [12] This article addresses both the network analysis of the polarizer and the device’s role in improving rf pulse compressor technology at SLAC National Accelerator Laboratory
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